lefty3382

So I've been dealing with this problem for months, since I discovered it in June or July. Since then I have spent hundreds of dollars and taken my car to 2 different shops, and still don't know what the problem is.

The problem presented itself when I stopped at a Subway one night for a sandwich. When I tried to start my car to go home the battery was dead. So I called my friend and we push started the car and I got it home. Through much trial and error, including a trip from LA to the Bay Area where I got stranded on a toll bridge, I discovered that running the car with the headlights on drains the battery within an hour or so. The battery also drains very slowly when it sits over a matter of days. But if I don't use the headlights and start the car regularly it runs okay.

I replaced the battery (twice), starter, starter solenoid, battery wires, and the alternator was only a couple months old when this started. Its a really nice 60 amp Powermaster chrome 1 wire unit. None of this helped. I have checked the wiring repeatedly for a short, bare wire, loose ground, anything at all. Can't find anything, but I'm not electrically inclined.

I took it to a mechanic in the North Bay and they tested my alternator and said the voltage regulator on the unit was bad. So I sent it back to SummitRacing and got an identical replacement unit. No difference. Same symptoms. And just yesterday I took it to Mustangs, Etc. in Van Nuys to have them look at it and they couldn't find anything wrong either. They checked the wiring, couldn't find a problem. They hooked a voltmeter to the alternator and I watched the level bounce from 13 to 14, then down to 12 with the headlights on while revving, then up to 15, all over the place, which would suggest a bad voltage regulator. Really? Two in a row? They then suggested I return the alternator again and get a different brand with a higher amp rating. If the problem still persisted, it would at least clear the alternator once and for all. Other than that, and continuing to check the wiring, I don't know what else to do.

I'm sure someone else has experienced something like this before, what in the heck is going on??

Gun Jam

I second the different choice of alt with perhaps higher output...

2 bad regs in a row isnt that far fetched...made in china right?

Happy hunting

-Gun

Nabster

In addition to a different alternator (the 60 amp, while about stock, seems a bit low on output) have you tried replacing the headlight switch? The headlights seem to be a player here, so it may not hurt to try a new ones of those.

cdan03

i believe one wire alternators have things called cut ins. at a certain rpm the alternator will work and start charging. generally it is around 1200 rpms. so at idle you will be running on battery.

i have a tuff stuff 140 amp one wire alternator and love it. i haven't had any problems with it since i bought it. it has a 800 rpm cut in.

did you leave the car running when you were at subway? also, do you have anything added on to the car other than stuff from the factory (big sound system, electric fan, electric fuel pump etc.).

lefty3382

i did not leave the car running while in subway. my only addition to the electrical system beyond stock is a mild stereo system consisting of a deck and 4 speakers. I have not turned the stereo on since this problem began.

I'll try a Tuff Stuff alternator the next time around. I'm not sure how much extra power my stereo system requires, but a 140 amp alternator seems like a bit overkill. Can you do damage by getting too strong an alternator? Maybe I'll try the 100 amp model.

I'll also look into putting in a new headlight switch.

hiboostwoody

Check ALL the headlight wiring. From the switch to the dimmer switch to the headlights. I also think you should try a higher amp alternator. Using one that is mega amp rated like the 140 will not harm your battery. It only means that the alternator won't have to work as hard to do it's job.

2+2GT

OK, you should be seeing a steady 14.2V. Looks like your alternator is crap. Why are you changing to this 1-wire junk? The OE stuff works fine.

67 evil eleanor

I would look at the RPM's the alt is turning at idle. Sometimes the drive pully may be too small and the alternator will not turn fast enough to "cut in".


"This could be caused by several things. First, the pulley ratio may cause the alternator to spin too slow for these driving conditions. Using underdrive or power pulleys on a street application can cause this problem because the pulley ratio becomes less than the typical street ratio of 3:1. If the pulley ratio IS 3:1, another possibility is that the alternator is too small or not powerful enough at slow speed for the amp load of the vehicle. Also, the charge wire could be too small or the ground path may have high resistance. The gauge could be out of calibration. Check the voltage directly at the alternator with electrical loads on to determine if the problem is the alternator or the path to the battery."

A easy way to check this is to turn up the idle and see what happens. You can check the ratio by using a string around the pulley's and dividing.
Also keep in mind that at lower rpms the alternator output may not be able to keep up with the demand of the electrical system, increasing the rpms via a different pulley may solve the problem. Also wire size fron the alternator can be too small and this could lower the current. Normally a 4 AWG on this short run will do (3' or less).

lefty3382

Okay, maybe I'll go with the 140 amp just to be safe, a Tuff Stuff 140 amp costs about the same as my Powermaster 60 amp anyway. I switched to this 1 wire "junk" because being the electrical novice that I am, I take any opportunity I can to simplify my electrical system and clean up my engine bay. Moving from 3 wires to 1 and eliminating the voltage regulator as a separate part seemed like a logical way to do this. I had a 1 wire Powermaster 140 amp unit a few years ago when I had a major sound system in the car, and I never had any problems with it. I'm sorry I sold it.

I don't think the problem has to do with the alternator cut in, considering the battery drain problem occurs A) when driving with the headlights with the RPM's way above idle, and B) when the car is off. To me, the former combined with the voltmeter readings at the shop suggest an alternator/regulator problem, and the latter suggests a drain/short in the wiring somewhere.

I have 2 AWG wire for both battery cables, the starter to solenoid cable, and the battery to solenoid cable.

2+2GT

Have you checked for current draw with the ignition "off"?